1. Field
This relates to a light emitting device, a light emitting device package, and a lighting system including the light emitting device package.
2. Background
Light emitting devices (LEDs) are semiconductor devices that convert electricity into light. Commercialized red LEDs and green LEDs have been used as light sources for electronic devices such as, for example, information and communication devices.
Nitride semiconductors have high thermal stability and wide band gap and may be used together with other elements such as indium (In) and aluminum (Al) for fabricating semiconductor layers capable of emitting green, blue, and white light, and emission wavelengths of nitride semiconductors may be relatively easily adjusted. In the field of nitride based LEDs, attempts to improve semiconductor growth structures or processes of growing epitaxial layers have been recently made to develop optical devices having high light extraction efficiency.
The efficiency of an LED chip may be determined by internal quantum efficiency, light extraction efficiency, and current injection efficiency. The current injection efficiency is relate to electric resistance and applied voltage, and thus a reduction in resistance of the LED chip may to increase the current injection efficiency.